Tobacco sheet of high wet strength



United States Patent 3,499,453 TOBACCO SHEET OF HIGH WET STRENGTH JohnTownend, Lancaster, Pa., assignor to General Cigar Co., Inc., New York,N.Y., a corporation of New York No Drawing. Original application Dec. 1,1966, Ser. No. 598,215, now Patent No. 3,416,537, dated Dec. 17, 1968.Divided and this application July 10, 1968, Ser.

Int. Cl. A24b 13/00 US. Cl. 131--17 4 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to the manufacture of coherent tobacco productssuitable for smoking and more particularly to such tobacco products inthe form of a leaf or foil with an appearance and other physicalqualities that they may be applied as the outer wrapper of cigars,cigarillos and the like in lieu of leaf tobacco ordinarily used as suchwrapper. A feature of the new tobacco products is high resistance todisintegration when moistened and even chewed.

In essence, tobacco products of high wet strength are made of comminutedtobacco and film-forming cellulose derivatives which are substantiallyinsoluble in water at normal (25 C.) and higher temperatures but aresubstantially soluble in organic acid of not less than about 15% byweight concentration in water. Preferably, the water-insoluble cellulosederivative is dissolved in formic or acetic acid of about to 40% byweight concentration in water. While a tobacco sheet produced simply byadmixing dry-ground tobacco powder with a solution of a cellulosederivative in acetic acid, casting and drying the resultant tobaccosuspension will have high wet strength, such tobacco sheet will not haveadequate resistance to chewing particularly when used as wrapper onlarge cigars that are frequently subjected to excessive chewing by somesmokers. However, where chew resistance in addition to wet strength isdesired in a tobacco sheet, this is achieved pursuant to the inventionby in corporating in the suspension of tobacco in acetic acid highlyhydrated, well-beaten cellulose fibers which may be derived fromtobacco, particularly tobacco stems, or other plants as is known in thepulp art.

The particularly valuable tobacco sheets which include cellulose fibersfor chew resistance have been made possible by the dual nature of thesolvent used in accordance with this invention which combines organicacid to dissolve the water-insoluble cellulose derivative with water tohydrate the cellulose fibers.

BACKGROUND OF INVENTION This is a division of application Ser. No.598,215, filed Dec. 1, 1966, now Patent No. 3,416,537.

There has long been a need for tobacco sheets of high wet strength andgood chew resistance, particularly for use as wrappers on cigars.Numerous proposals have been made but none has been completelysatisfactory.

Detert et al. first disclosed in US. Patent 2,893,400 a tobacco sheetfor use as cigar wrapper made fromfinely pulverized tobacco andmethylcellulose dissolved in an anhydrous solvent consisting of amixture of methanol and methylene chloride. However, these patenteesadmitted the low wet strength of their tobacco sheet in U.S. Patent2,927,588 wherein they proposed the addition of phosphoric acid to themixture of finely pulverized tobacco and an anhydrous solution ofmethylcellulose. The addition of phosphoric acid was alleged to have thesurprising result that the resistance of the tobacco foils to tearing,their resistance to water, and their stability in storage are improvedto such an extent that they can be manipulated without difficulty eitherby hand or by machines. Interestingly enough, the patentees still didnot allege that their tobacco sheet had any chew resistance and theyfailed to take into account that phosphoric acid is known to be acombustion retardant.

In still another effort to find a satisfactory process, Detert et al.later suggested in US. Patent 3,062,688 that finely pulverized tobaccobe mixed with a solution of a combination of water-solublemethylcellulose and a waterinsoluble cellulose derivative in an organicsolvent consisting of a mixture of methylene chloride and methylalcohol. The tobacco foil thus produced was alleged by the patentees toovercome the disadvantages of their prior foils which, in the words ofthe patentees, do not meet the high requirements of cover leaves forcigars and cigarillos with respect to their resistance to tearing and tosaliva, and also because they have not suflicient suppleness. However,even this latest proposal of Detert et al. fails to :produce a tobaccosheet of sufficiently high wet strength and chew resistance to beacceptable as wrapper on cigars that are subjected to wet-chewing bymany smokers.

Another approach to the same problem has been the concept of producingtobacco sheets with water-soluble binding or film-forming agentstogether with cross-linking agents which are intended to render theresultant tobacco sheet water-insoluble. Thus, it was proposed in US.Patent 2,769,734 that a water-soluble binding agent be cross-linked byglyoxal. US. Patent 2,887,414 disclosed the use of dialdehyde starch ascross-linking agent for a water-soluble binding agent, while US. Patent3,- 106,212 suggested the use of moisture resistance agents such asmelamine formaldehydes and urea formaldehydes with water-soluble bindingagents to produce moisture resistant tobacco sheets. These and othersimilar proposals have proved to be unsatisfactory for such reasons aspoor smoking taste arising from the use of the crosslinking agents,darkening of the tobacco by the crosslinking agents, instability of thewater resistance of the tobacco sheets during prolonged storage, andstiifening of the tobacco sheets to an extent that they fail to conformsatisfactorily when applied as wrappers on shaped cigars.

DESCRIPTION OF INVENTION Fundamental to the invention is the selectionof an aqueous solution of organic acid as the solvent for cellulosederivatives which are known to be binding agents or film-formers butwhich are substantially insoluble in water at normal (25 C.) or highertemperature. The organic acid must be completely miscible with water andvolatile at temperatures which may be used to dry the tobacco productwithout substantial impairment of its smoking quality. Formic and aceticacids best fulfill these requirements of the organic acid used assolvent. Acetic acid is preferred particularly inasmuch as it is lessexpensive than formic acid. While aqueous organic acid with as low as15% by weight concentration and as high as concentration may serve assolvent, the preferred solvent is generally in the range of about 20% to40% by weight of formic or acetic acid in water.

The water-insoluble cellulose derivative chosen for the production of atobacco sheet or other coherent form must be soluble at normaltemperature in the aqueous organic acid used as solvent. Since thepreferred solvent is aqueous formic or acetic acid in the range of about20% to 40% by weight concentration, the preferred waterinsolublecellulose derivatives are those which are substantially soluble in suchsolvent even though water-insoluble cellulose derivatives requiringaqueous formic or acetic acid of as high as about 80% by weightconcentration may be used pursuant to this invention. It is well to notethat generally the dissolving of the water-insoluble cellulosederivative is preferably carried out by initially using an organic acidof higher concentration than is ultimately desired for the production ofa tobacco sheet or other coherent form of tobacco, and then adding waterto the solution to bring the concentration of the organic acid to thedesired value. Many of the water-insoluble cellulose derivatives usefulpursuant to this invention requires this dissolving procedure becausethey are not adequately dissolved by direct suspension, say, in aqueousacetic acid of about 20% to 40% by weight concentration but they remainsubstantially in solution when their solutions in glacial acetic acid orin concentrated acetic acid, e.g., about 80% by weight concentration,are diluted. with water to acetic acid solutions of about 20% to 40% byweight acid concentration.

The organic acid used as solvent pursuant to this invention may be notonly a mixture of formic and acetic acids but also a mixture of eitheror both of these acids with a somewhat less volatile acid like propionicacid or even a substantially nonvolatile acide like lactic or citricacid. Poorly volatile and nonvolatile acids are used as only the minorcomponent in admixtures with formic or acetic acid. The use of a minorproportion of an nonvolatile acid such as malic or tartaric acid as wellas lactic or citric acid serves the dual purpose of acting as part ofthe organic acid solvent for the water-insoluble cellulose derivativeand of plasticizing the tobacco product to render it more flexible andworkable in making cigars especially when the product is a tobacco sheetapplied as cigar wrapper. Generally, such acids that remain in a tobaccoproduct made pursuant to this invention are used in an amount notexceeding about 20% by weight based on the tobacco content of theproduct. Even at such a comparativel high level of acid in the tobaccoproduct, hydroxylated polycarboxylic acids in particular have been foundto be not objectionable during the smoking of the tobacco product.

Dry-ground or pulverized tobacco may be formed into a coherent formhaving appreciable wet strength with the aid of a water-insolublecellulose derivative dissolved in aqueous formic or acetic acid. In suchcase where no fiber is present in formulating the tobacco product, theuse of a minor amount of plasticizing acid such as citric or lactic aspart of the aqueous organic acid is generally advisable inasmuch as theplasticizing acid tends to prevent cracking especially when the productis a tobacco sheet. However, considerably higher wet strength may beobtained by incorporating in the formed tobacco product highly hydrated,well-beaten cellulose fibers. The pulp of refined cellulose fibers maybe prepared from tobacco, particularly stems, or from the usual sourcesused in the pulp industry. In terms of the improved physical properties,especially tensile strength, of a tobacco sheet achieved byincorporating a certain weight percentage of refined fibers of thesulfite or sulfate type pulp, generally at least twice as much refinedfibers derived from tobacco stems are required for the same improvedproperties.

The selection of the water-insoluble cellulose derivative to be used asbinding agent is based not only on its solubility in aqueous organicacid, especially acetic acid, but also on its viscosity when sodissolved. A water-soluble cellulose derivative like methylcellulose maybe made water-insoluble by increasing the degree of substitution ofhydroxyl hydrogen in the original cellulose molecular chain withhydrophobic substituents like methyl, ethyl and acetyl. However, it isknown that the cellulose molecular chain tends to degrade or break intoshorter chains as the degree of substitution is increased. Since thebinding or film-forming capacity of cellulose derivatives in tobaccosheets and other coherent bodies generally decreases as the cellulosemolecular chains become shorter, it is important for the purposes ofthis invention to select cellulose derivatives in which the degree ofsubstitution has been increased, just enough to make the cellulose de- 4rivative substantially water-insoluble without degrading the molecularchains to an extent that the binding capacity of the cellulosederivative has been seriously impaired.

The length of cellulose molecular chains, commonly referred to as degreeof polymerization, is frequently determined by the viscosity of thecellulose derivative in a given solvent, at a given concentration and ata given temperature. Thus, the degree of polymerization or viscositygrade of a water-soluble cellulose derivative like methylcellulose isusually established by the viscosity in centipoises (cps.) at atemperature of 20 C. for a water solution containing 2% by weight of thecellulose derivative. For the water-insoluble cellulose derivatives usedin accordance with this invention, it has been found to determine thedegree of polymerization, hereinafter called the acid viscosity grade,by measuring in a Brookfield R.V.T. viscosimeter (speed 20 revolutionsper minute) the viscosity at a temperature of 25 C. of 1% by weight ofthe cellulose derivative dissolved in aqueous acetic acid having anacetic acid content of by weight. Generally, the water-insolublecellulose derivative used pursuant to this invention is desirably onehaving an acid viscosity grade of at least about cps. and preferably atleast about 250 cps.

Water-insoluble cellulose derivatives suitable for the purposes of thisinvention include water-insoluble grades of methylcellulose,ethylmethylcellulose, ethylcellulose, ethylhydroxyethylcellulose andcellulose acetate. Another group of suitable binding agents compriseswater-soluble grades of cellulose derivatives such as methylcellulose,hydroxyethylcellulose, methylhydroxyethylcellulose,ethylhydroxyethylcellulose, methylhydroxypropylcellulose andmethylhydroxybutylcellulose which have been acetylated to the extent ofrendering the cellulose derivatives substantially insoluble in water atnormal and higher temperatures. For example, water-solublemethylcellulose of 8000 cps. viscosity grade (2% by weight in water at atemperature of 20 C.) and having a methoxyl content of about 30% byweight that has been acetylated to the extent that the cellulosederivative has an acetyl content of between about 5% and 12% by weighthas been found to be substantially water-insoluble but soluble inaqueous acetic acid of about 20% to 40% by weight concentration.

It should be noted that the Water-insoluble cellulose derivatives usefulfor the purposes of this invention embrace not only the commerciallyavailable types that are soluble in the conventional organic solventssuch as a mixture of methylene chloride and methanol but also speciallyprepared types that are generally considered unsatisfactory for solutionin such conventional organic solvents. For instance, commerciallyavailable ethylcellulose has an ethoxyl content of over about 44% byweight and cellulose acetate has an acetyl content of over about 37% byweight; such cellulose derivatives are soluble in aqueous formic oracetic acid of about 80% by weight concentration. On the other hand,ethylcellulose and cellulose acetate made with, respectively, lowerethoxyl and acetyl contents (but not low enough to make these cellulosederivatives substantially soluble in water) are soluble in lessconcentrated aqueous formic or acetic acid with an acid content goingdown to about 15% by weight.

The specially made cellulose derivatives in contrast to the types whichare commercially produced for solution in conventional organic solventsoffer the advantages of obviating the use both of such highlyconcentrated organic acid as aqueous acetic acid of 80% by weightconcentration and of the comparatively larger proportion of highlyhydrated, refined cellulose fibers required to prevent cracking of atobacco sheet during its manufacture with a cellulose derivative of thetype olfered commercially for solution in conventional organic solvents.Moreover, a tobacco sheet made with the latter type cellulose derivativeis usually not suificiently plasticized by water to make it stretchableenough for use as wrapper on cigars of the pcrfectO or like Shapes; insuch case, a

water-soluble or highly water-susceptible binding agent is desirablyused together with the cellulose derivative so that the resultingtobacco sheet can be plasticized by water to give it the desired degreeof stretch or elasticity.

While humectants and plasticizers such as glycerol, sorbitol and variousglycols are generally used in tobacco smoking products to avoidexcessive drying and embrittlement, it is noteworthy that tobacco sheetsand other coherent bodies of tobacco produced in accordance with thisinvention rarely require the use of humectants or plasticizers becausewater alone is an adequate plasticizer. It has been known that tobaccosheets with a high moisture content, usually over by weight, are duringprolonged storage susceptible to deterioration in one form or anothersuch as loss of strength, change of appearance or even mold formation.By contrast, the tobacco sheets of this invention may be made with acomparatively low moisture content, say about 20% by weight, so as tohave good stability during prolonged storage. While such tobacco sheetswill have poor elasticity, this physical limitation is easily correctedat the time such tobacco sheets are being utilized in the manufacture ofa smoking product, such as wrapper on cigars, by moistening with water.The tobacco sheets of the invention may be moistened by a water spray,by contacting a wet roller or even by dipping. The moistening of thetobacco sheets with :water is desirably controlled so that the moisturecontent then generally is in the range of about to by weight inasmuch assuch moistened tobacco sheets have the necessary stretch and otherphysical properties to be successfully applied as wrappers on cigars ofeven intricate shapes. Obviously, the amount of water added to a tobaccosheet need not be more than that just required to make the workabilityof the tobacco sheet satisfactory for its intended use such as Wrapperon cigars.

When a tobacco sheet is to be applied as the outer covering or wrapperof a cigar, the addition of an ashwhitening material like titaniumdioxide and an ashstrengthening agent like comminuted ceramic fiber tothe basic components of the tobacco sheet may be advisable.

The coherent tobacco products of this invention may be used incigarettes, pipe tobacco and like smoking products but the high wetstrength and chew resistance that may be achieved in tobacco sheets madeby this invention clearly indicate that such tobacco sheets areespecially attractive for use as wrappers on cigars. Hence, furtherelaboration of the invention will be made in terms of its most valuablecommercial application, namely, tobacco sheets used as wrappers oncigars.

For a better understanding of the invention and its scope, illustrativeembodiments are presented hereinbelow in detail. In the examples,proportions are given in parts and percentages by weight unlessotherwise specified.

EXAMPLE 1 Burley tobacco stems cut to pieces of about 1 inch in lengthwere admixed with water to form a 7.4% suspension which was placed in asealed autoclave for treatment in accordance with the process of US.Patent 3,076,79 to Garbo. Approximately 25% of the volumetric capacityof the autoclave was charged with commercially pure oxygen at an initialpressure of 700 p.s.i.g. (pounds per square inch gauge). While stirring,the stem suspension was heated until a temperature of about 300 F. wasreached and then this temperature was maintained for a 20-minute periodduring which the pressure was held at about 1200 p.s.i.g. with the helpof added oxygen when needed. Thereupon, the suspension in the autoclavewas rapidly cooled to a temperature of about 175 F. and discharged at apressure of about p.s.i.g. through a Rietz disintegrator fitted with ascreen having -inch openings.

The thus treated suspension was filtered to discard the liquid and theresidual stem material was so washed on the filter that the dry solidsof the washed stem material had a ratio of total solids towater-insoluble solids, hereinafter called the wash ratio, of 1.2. Thewashed stem material was again dispersed in water to form a 6%suspension based on the dry solids of the washed stem material and thissuspension with added titanium dioxide was repeatedly passed through adisc refiner until the refined stem fiber had a reverse freeness of 70as determined by the S-chopper-Riegler type beating and freeness tester.The titanium dioxide which was added to the stern suspension in theratio of 1 part to 12.5 parts of dry solids in the suspension served twopurposes, namely, lightening the color of the finished tobacco sheet andyielding a whitish ash ash when the tobacco sheet was smoked as wrapperon a cigar.

The refined pulp of Burley stems was admixed with water-insolublemethylcellulose (39.5% methoxy content) having an acid viscosity gradeof 310 cps. that had been dissolved in aqueous acetic acid and wasfurther admixed with a dry-ground blend of cigar-type tobacco basedprincipally on Wisconsin tobacco. The pulverized tobacco blend passedthrough -mesh screen (U.S. Sieve size) but only 85% passed throughZOO-mesh screen. To strengthen the ash of the tobacco, a ceramic fiber(Fiberfrax sold by The Carborundum Company), which was cut to very shortfragments while suspended in water by a high-speed, high-shear stirrer,was also added to the pulp of Burley stems. The proportioning of theadmixed components was such that the final slurry contained:

Parts Pulverized tobacco blend 150 Refined Burley stems (dry solids)Water-insoluble methylcellulose 40 Titanium dioxide 10 Ceramic fiber 3all in 20% aqueous acetic acid at a total concentration of 5.9% of theaqueous acetic acid. The final slurry had a viscosity of 7000 cps. at atemperature of 10 C.

This slurry was spread evenly on a stainless steel belt which wassubsequently heated first with hot air impingement on the slurry-coatedbelt and as soon as enough water and acetic acid had been removed byevaporation to set the slurry coating on the belt was further heatedwith steam condensation on the underside of the steel belt. The driedcoating on the belt was rehumidified to a moisture content of about 35%and stripped from the belt as a tobacco sheet. The moisture content wasdecreased to about 20% with the aid of infrared lamps and the tobaccosheet approximately 0.002 inch thick was then wound up in rolls suitablefor use on a cigar-making machine.

The tobacco sheet had a pleasing appearance and a brown color similar tothat of some grades of cigar wrapper leaf tobacco. The Finch tensilestrength of this tobacco sheet, determined according to ASTM standardtest D829-48, using an immersion time of 30 seconds in water and a testsample of double width, was 125 g./mm. (grams per square millimeter).

Perfecto-shape cigar bunches were wrapped with this tobacco sheet afterincreasing its moisture content to about 45% since at this high moisturecontent the tobacco sheet had good stretch so that it could be pulledover the curved portions of the perfecto-shape cigar bunches and thusconform to the shape without forming gaps or creases in the wrappersheet. At the time of application of the tobacco sheet as cigar wrapper,an odor of acetic acid was noticed because of the volatilization of asmall residue of acetic acid in the tobacco sheet as stripped from thestainless steel belt. However, after the finished cigars were dried toan average moisture content of about 13 the odor of acetic acid hadvanished.

The perfecto-shape cigars with the tobacco sheet wrapper were found toburn with an attractive whitish, firm ash and to have a very agreeablesmoke taste. Smokers who are accustomed to chewing a cigar while smokingit noted that this tobacco sheet wrapper withstood chewing better thanmost tobacco leaf wrappers.

EXAMPLE 2 Burley tobacco stems processed as in Example 1 but refined toa reverse freeness of 92 were passed from the disc refiner once througha valve-type homogenizer at a pressure of 4500 p.s.i.g. Only 1 part oftitanium dioxide was added to 100 parts of dry solids in the tobaccostem suspension prior to refining this suspension.

Ethylcellulose of 35.5% ethoxyl content was dissolved in aqueous aceticacid of 70% by weight concentration and was admixed with a dry-groundblend of 50% Sumatra and 50% Santo Domingo tobaccos, all passing through100-mesh screen. The components were admixed to give a final slurrycontaining:

Parts Pulverized tobacco blend 150 Refined Burley stems (dry solids) 100Ethylcellulose 50 Titanium dioxide 1 all in 45% aqueous acetic acid at atotal concentration of 6% of the aqueous acetic acid.

This slurry was converted into a tobacco sheet as described inExample 1. The appearance and physical roperties of this tobacco sheetwere comparable to those of the tobacco sheet of Example 1.

Blunt-shape cigars were made with the tobacco sheet of this example aswrapper. The cigars had the typical appearance of moderate-priced cigarsand, in smoking tests, were found to have considerable chew-resistanceand a pleasing smoke taste.

EXAMPLE 3 The Burley stems of Example 1 were first passed through heatedrolls moving at differential speeds which flattened and tore the stempieces to yield a product in chip form, called flaked stems. The flakedstems were suspended in water, autoclaved and further processedincluding washing to a wash ratio of 1.1 as described in Example 1. Thewashed stem material with the added titanium dioxide was refined andhomogenized as described in Example 2.

The thus prepared Burley stems were dewatered to a solids content of 15%and added slowly with high agitation to a solution of a mixture of 37.5parts of methylcellulose (39% methoxyl content) and 12.5 parts ofethylcellulose (45% ethoxyl content) in glacial acetic acid until 100parts (dry solids basis) of the stem material had been added. Water wasthen added slowly under high agitation to bring the acetic acidconcentration to 80%. Finally, 100 parts of a blend of dry-groundWisconsin tobacco and tobacco fines from cigar manufacture were added.The resulting slurry, having a solids content of 4.5% and a viscosity of21,000 cps. at 20 C., was formed into a tobacco sheet as described inExample 1. The product was light in color, resembling a desirable cigarWrapper, and had properties suitable for conformance to shaped cigars.

EXAMPLE 4 The procedure in Example 3 was followed in all details exceptthat in place of 37.5 parts of the water-insoluble methylcellulose, 25parts of water-soluble methylcellulose (30% methoxyl content) of 1500cps. viscosity grade was used, while the quantity of the ethylcellulosewas doubled to 25 parts. The resulting tobacco sheet in appearance,physical properties and smoking qualities was very satisfactory as acigar wrapper.

EXAMPLE 5 Flaked Burley stems were processed as in Example 3 except thata conical refiner was used instead of the disc refiner. To a solution of50 parts of ethylmethylcellulose with a degree of substitution of 0.94ethyl and 1.34 methyl (acid viscosity grade of 110 cps.) in glacialacetic acid were added 100 parts (dry solids basis) of the refined andhomogenized Burley stem material. Sufficient water was added to bringthe acetic acid concentration to 30% and then 150 parts of dry-groundSumatra tobacco were admixed to yield a slurry containing 7.5% solids.After deaeration, the slurry had a viscosity of 12,800 cps. at atemperature of 11 C.

The slurry was converted to a tobacco sheet as described in Example 1.The resulting tobacco sheet had good cigar wrapper properties includingattractive color and texture. Panatella-shape cigars made with thiswrapper sheet withstood considerable chewing during smoking tests inwhich the smoke taste was rated very good.

EXAMPLE 6 The processed Burley stems of Example 3 were added to theextent of 50 parts (dry solids basis) to a solution of 20 parts ofacetylated methylcellulose (prepared by acetylating water-solublemethylcellulose of 8000 cps. viscosity grade to 8% acetyl content) inglacial acetic acid. Sufficient Water was added to bring the acetic acidconcentration to 35% and then 150 parts of dry-ground Java tobacco wereadmixed to yield a slurry with a solids content of 7% and a viscosity of6500 cps. at 30 C.

The tobacco sheet formed from this slurry as described in Example 1,having an unusually high tobacco contact (91% dry basis), had a tensilestrength of 495 g./mm. and a Finch tensile strength of 75 g./mm. Itsperformance as a cigar wrapper was very satisfactory.

EXAMPLE 7 Cellulose fibers (fully bleached sulfate softwood pulp) weredispersed in water at a dry solids concentration of 3% and passedrepeatedly through a disc refiner until a Schopper-Riegler reversefreeness of 47 was attained. Eighty parts .of acetylated methylcellulose(8.4% acetyl content, 28% methoxyl content, acid viscosity grade of 920cps.) were dissolved in 4940 parts of 70% aqueous acetic acid. Twentyparts of water-soluble methylcellulose (8000 cps. viscosity grade) weredissolved in the same acetic acid solution.

The refined cellulose fiber slurry was added to the extent of parts (drysolids basis) to the aqueous acetic acid solution of the cellulosederivatives under high agitation. Then 15 parts of titanium dioxide, 5parts of fragmented Fiberfrax and 800 parts of Connecticut shade wrappertobacco cuttings, which had been dry-ground so that 100% passed through100-mesh screen and passed through 200-mesh screen, were uniformlydispersed in the cellulose fiber slurry. The entire mixture was dilutedwith 3690 parts of water to bring the acetic acid concentration to 30%.The viscosity of the final mixture was 6600 cps. at a temperature of 21C.

The tobacco sheet produced from this final mixture as described inExample 1 was found to be adequate in all respects as a cigar wrapper.

EXAMPLE 8 Flaked Connecticut shade tobacco stems were suspended in waterat a concentration of 7.5 autoclaved, filtered, washed and refined asdescribed in Example 1. A 4% solution in 50% aqueous formic acid wasprepared of a mixture of acetylated methylcellulose (8.4% acetylcontent, 28% methoxyl content, acid viscosity grade of 360 cps.) andwater-insoluble methylcellulose having 40.3% methoxyl content (acidviscosity grade of 345 cps).

A slurry of refined cellulose fibers was prepared as described inExample 7. The processed Connecticut shade tobacco stem slurry and therefined cellulose fiber slurry were mixed together and added to theaqueous formic acid solution of the cellulose derivatives. To this mixedslurry, dry-ground Connecticut shade wrapper tobacco cutting asdescribed in Example 7, Fiberfrax, and titanium dioxide were added. Thefinal slurry had 7% solids in aqueous formic acid of 40% concentrationand contained:

Parts Processed Connecticut shade tobacco stems (dry solids) 20.0Refined cellulose fibers (dry solids) 10.0 Ground Connecticut shadewrapper tobacco 55.0 Acetylated methylcellulose 3.0 Water-insolublemethylcellulose 9.5 Fiberfrax 0.75 Titanium dioxide 1.75

The final slurry was converted into a tobacco sheet having a dry weightof 35 g./m. (grams per square meter), a tensile strength of 870 g./mm.and a Finch tensile strength of 170 g./mm. Used as a cigar wrapper, theproduct had high chew resistance and pleasing smoking qualities.

EXAMPLE 9 To 1358 parts of a 6% solution of cellulose acetate (about 28%acetyl content) in aqueous acetic acid of about 40% acid content wereadded 2260 parts of glacial acetic acid. To this solution were added1250 parts of a 3.6% aqueous solution of water-soluble methylcellulose(30% methoxyl content) of 1500 cps. viscosity grade, 35 parts of a 50%aqueous slurry of titanium dioxide, 7.5 parts of fragmented Fiberfrax,and 1462 parts of water. Then 4000 parts of the aqueous slurry ofrefined cellulose fibers prepared as described in Example 7 but dilutedto a dry solids concentration of 2.5% were added. Finally, 750 parts ofa dry-ground mixture of Wisconsin tobacco and tobacco fines resultingfrom cigar manu facture were thoroughly blended into the total slurrywhich was diluted with 2000 parts of water to adjust the acetic acidconcentration to 30% and the viscosity to 5500 cps. at a temperature of21 C.

The tobacco sheet made from this final slurry as described in Example 1had a dry weight of 37 g./m. and a Finch tensile strength of 190 g./m.This product had the desirable characteristics of good cigar wrapper tobacco.

EXAMPLE 10 To 75 parts of acetylated hydroxyethylcellulose (degree ofsubstitution of 1.5 acetyl, molecular substitution of 1.1 hydroxyethyl)slurried in 750 parts of water were added under agitation 1890 parts ofglacial acetic acid. To the resulting solution were added 1000 parts ofwater, 4.5 parts of fragmented Fiberfrax, and 21 parts of a 50% aqueousslurry of titanium dioxide. Next, 1720 parts of the aqueous slurry ofrefined cellulose fibers prepared as described in Example 7 butconcentrated to a dry solids content of 3.5% and 450 parts of dry-groundConnecticut shade wrapper tobacco as described in Example 7 were blendedwith the solution of cellulose derivative. The total slurry was dilutedwith 990 parts of water so that the final acetic acid concentration was30% and the viscosity of the slurry was 7000 cps. at C.

The tobacco sheet made from this slurry as described in Example 1 wasattractive in appearance and served as a cigar wrapper of good smoketaste and chew resistance.

EXAMPLE 11 A mixture of 3 parts of acetylated methylcellulose (9.3%acetyl content, 28% methoxyl content) and 9.5 parts of water-insolublemethylcellulose (39.5% methoxyl content) was suspended in 60 parts ofwater and under high agitation 303 parts of glacial acetic acid wereadded. To the resulting solution were added 10 parts (dry solids basis)of autoclaved, filtered, washed, and refined Connecticut shade tobaccostems as described in Example 1 and 55 parts of Connecticut shadewrapper tobacco ground so that 100% passed through 100-mesh screen and60% passed through ZOO-mesh screen together with 20 parts of Connecticutshade tobacco stems ground so that 100% passed through -mesh screen andpassed through ZOO-mesh screen. To this mixture were added 1.75 parts oftitanium dioxide and 0.75 part of comminuted Fiberfrax. Sufiicient waterwas added to the total mixture to bring the acetic acid concentration to30%, the solids content to 9% and the viscosity to 11,400 cps. at atemperature of 7.5 C.

The tobacco sheet made from the final mixture had a pleasing color,comformed well to shaped cigars and was as chew resistant as wrappertobacco of good quality.

EXAMPLE 12 Flaked Burley stems were cooked as a 12.3% suspension inwater in a heated kettle with stirring for one hour at a temperature of120 F. This suspension was then passed through a Rietz disintegratorfitted with a screen having ;-inch openings, filtered and washed to awash ratio of 1.2. The fibrous stem mass was redispersed in water togive a 5% suspension which was refined by 29 passes through a discrefiner and then one pass through a valve-type homogenizer at a pressureof 4500 p.s.i.g.

The thus processed Burley stems were slowly added under high agitationto a solution of 40 parts of waterinsoluble methylcellulose (39.5%methoxyl content) in 1630 parts of 80% aqueous acetic acid until 150parts (dry solids basis) of the processed stems were incoprated. Then150 parts of dry-ground Pennsylvania tobacco stems passed throughZOO-mesh screen) and 3 parts of fragmented Fiberfrax were added underhigh agitation. The mixture was slowly diluted under high agitation'with water to reduce the acetic acid concentration to 30%. The finalslurry had a solids content of 6.8% and a viscosity of 16,000 cps. at 11C.

Tobacco sheet produced from the final slurry as described in Example 1had a good light-brown color and performed satisfactorily in allrespects as a cigar wrapper.

EXAMPLE 13 Flaked Connecticut shade tobacco stems were processed asdescribed in Example 8. The resulting stem slurry was cooled to atemperature of 50 F. and added slowly with high agitation to a solutionof 3 parts of acetylated methylcellulose (5% acetyl content, 29%methoxyl content, acid viscosity grade of 560 cps.) in 400 parts ofglacial acetic acid until 97 parts (dry solids basis) of refined stemfibers were admixed.

The final slurry in aqueous acetic acid of 25% acid content was cast asa thin coating on a stainless steel belt with a doctor blade and thecoating was evaporated to dryness as the belt traveled over steam pandryers. The resulting dry tobacco sheet was rehumidified, stripped fromthe belt and rolled up as described in Example 1.

This tobacco sheet contained, on a dry basis, only 3% of cellulosederivative but had physical properties adequate for its use as achew-resistant cigar wrapper.

EXAMPLE 14 Seventy-five parts of dry-ground Connecticut shade wrappertobacco cuttings (100% passed through 100- mesh screen and 85% passedthrough ZOO-mesh screen) were dispersed in 900 parts of a solutioncontaining 25 parts of acetylated hydroxyethylcellulose (degree ofsubstitution of 1.5 acetyl, molecular substitution of 1.1 hydroxyethyl)in aqueous acetic acid of 40% acid content.

Tobacco sheet with a dry weight of 40 g./m. was produced from theresulting slurry as described in Example 1. This tobacco sheet had aFinch tensile strength of about g./mm. and good elasticity at a moisturecontent of 40%; it was a very acceptable wrapper on panatella-shapecigars.

EXAMPLE l5 Seventy-five parts of the tobacco powder described in Example14 were dispersed in 900 parts of a solution containing 25 parts ofacetylated methylcellulose (10.1%

acetyl content, 28% methoxyl content, acid viscosity grade of 70 cps.)in a mixture of methylene chloride and rnethanol in which the weightratio of the two solvents was 9:1, respectively.

Tobacco sheet with a dry weight of 50 g./m. was produced from theresulting slurry and had a tensile strength of 475 g./mm. and a Finchtensile strength of 130 g./mm As a cigar wrapper, this tobacco sheet wasvery similar to the product of Example 14.

Example 15 illustrates the aspect of the invention of using awater-insoluble acetylated cellulose derivative which was water-solubleprior to being acetylated. Tobacco sheets of high resistance todisintegration when moistened can be produced with such water-insolubleacetylated cellulose derivatives whether dissolved in aqueous organicacid as shown in Example 14 or dissolved in organic solvent as shown inExample 15. Other organic solvents suitable for Water-insolubleacetylated cellulose derivatives disclosed hereinbefore as beingeffective and desirable binding agents for the production of tobaccosheets include such solvent mixtures, preferably in the indicated weightproportions, as 9' ethylene chloride-1 ethanol, 4 benzene-1 methanol,and 10 acetone- 1 ethanol.

The foregoing examples are illustrative of the many possible variationsand modifications of the invention. The examples further show that thetobacco sheets of this invention can be utilized to satisfy thediflicult and exacting requirements of a good cigar wrapper. Suchtobacco sheet can be made predominantly of comminuted tobacco whichwholly or in part has been ground in essentially a dry form or in theform of a liquid suspension. The tobacco content of such tobacco sheetsis generally not less than 75% by weight on a dry basis and frequentlyexceeds about 80%. The non-tobacco added components of these tobaccosheets, principally the cellulose derivative used as the binding agentand, in some cases, cellulosic fiber derived from plants other thantobacco such as softwood pulp, are present in minor proportions usuallynot exceeding 25% by Weight of the dry tobacco sheet and frequently lessthan about 20%. The substantially water-insoluble methylcellulose foundto be eflective in producing a cigar wrapper type of tobacco sheet isone having a methoxyl content of at least about 38% by weight. As alsodemonstrated by the examples, ash-improving components such as titaniumdioxide and finely divided ceramic fiber are effective 'when present tothe extent of only a few percent, generally less than 3%, of the weightof the dry tobacco sheet.

I claim:

1. A tobacco sheet of a chewable cigar wrapper type comprising a majorproportion of comminuted tobacco, a minor proportion of cellulosicfibers which had been highly hydrated by refining to a reverse freeness,and a minor proportion of water insoluble acetylated form of anOriginally water-soluble cellulose derivative.

2. The tobacco sheet of claim 1 wherein a minor proportion ofwater-insoluble methylcellulose with a methoxyl content of at least 38%by weight is present.

3. The tobacco sheet of claim 2 wherein the refined cellulosic fiberswere derived predominantly from tobacco stems.

4. The tobacco sheet of claim 2 wherein the acetylated form of cellulosederivative is selected from the class consisting of acetylatedmethylcellulose and acetylated hydroxyethylcellulose.

References Cited UNITED STATES PATENTS 3,042,552 7/1962 Rosenberg et al.131-17 3,062,688 11/1962 Detert et al. 131-17 3,322,130 5/1967 Panzer etal. 131-17 MELVIN D. REIN, Primary Examiner U.S. Cl. X.R. 131-140 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 99, 453 DatedMarch 10, 1970 Inventor(s) John Townend It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 3, line 10, "quires should read -quire--; line 22, "nonvolatileacide" should read --nonvolatile acid--; line 23, "nonvolatile" shouldread --non-volatile-; line 25, "an nonvolatile" should read --anonvo1atile--. Column 4, line 14, "found to should read --founddesirable to--; 4 line 72, "type" should read --type of--.

Column 5, line 43, "tobacco" should read --tobaccos--. Column 6, line14, "ash ash" should read -ash--; line 17, "methoxy" should read--methoxyl--; line 21, "tobacco" should read --tobaccos--; line 24,"tobacco," should read -tobacco sheet, Column 9, line 40, "190 g. /m.should read --19o g. /mm. Column 10, line l3, "l2. 3%" should read --l2.5%--.

SEALED swam ( Attest:

Edward M. Fletcher, 11:. WILLI 5am, JR. Arresting Officer 1 of PatentsFORM PO-IOSO (IO-69] uscomwuc 003mm Q 05. GDVIINMENY PIINYING OFFICE:I96 D-IGi-JJI

